1. Field of the Invention
The present invention relates generally to a device for and a method of detecting positioning marks in cutting a ceramic laminated body used for, for example, ceramic laminated electronic components, and more particularly, to a device for and a method of picking up an image in portions where positioning marks are formed and processing image information obtained to detect the position of a middle point of the positioning marks.
2. Description of the Prior Art
A ceramic laminated electronic component represented by a multilayer capacitor is formed by sintering a laminated body obtained by laminating a plurality of ceramic green sheets each having inner electrodes materials printed thereon and providing outer electrodes on the outer surface of a sintered body obtained. Generally, a plurality of mother ceramic green sheets each having inner electrodes printed thereon are laminated and a mother laminated body thus obtained is cut in the direction of thickness, thereby to obtain respective laminated bodies for a multilayer capacitor in order to increase productivity.
FIG. 2 is a plan view showing a mother ceramic green sheet as described above. A plurality of inner electrode materials 2 are printed with a predetermined pitch on the upper surface of the mother ceramic green sheet 1. In addition, positioning marks for cutting 3 are formed in the outer peripheral part of the upper surface of the mother ceramic green sheet 1. The positioning marks for cutting 3 are so formed as to have a predetermined positioning relationship with the inner electrodes 2.
In obtaining the respective laminated bodies for a multilayer capacitor, a plurality of mother ceramic green sheets 1 are laminated, to obtain a mother laminated body 4. Thereafter, the outer peripheral surface of the mother laminated body obtained is cut, to expose the positioning marks for cutting 3 to the outer side surfaces of the mother laminated body 4, as shown in FIG. 3.
As shown in FIGS. 4 and 5, the above described mother laminated body 4 is mounted on a cutting table 5. The cutting table 5 is constructed movably in the direction of the Y-axis and the direction of the .theta.-axis as shown. In the case of cutting, the positioning marks appearing on the outer side surfaces of the laminated body 4 are confirmed by the naked eye using cameras 7.
FIG. 6 shows a field of vision 8 for the cameras 7. In the case of cutting, the left end (indicated by a one-dot and dash line A) and the right end (indicated by a one-dot and dash line B) of a plurality of positioning marks for cutting 3 which are overlapped with each other in the direction of thickness are determined while observing the field of vision 8, and the middle between the left end and the right end, that is, a middle point (which exists on a line indicated by a one-dot and dash line C) is determined, to cut the mother laminated body 4 in a cutting position D (indicated by a broken line) spaced apart from the middle point by a predetermined distance on the basis of the middle point.
Meanwhile, when a cutting edge (not shown) is not located above the cutting position D, the cutting table 5 is moved in the direction of the Y-axis or the direction of the .theta.-axis such that the cutting edge is located directly over the cutting position D, to perform the cutting work.
In the above described conventional method of cutting a ceramic laminated body, however, the middle point of a group of the positioning marks for cutting 3 which are overlapped with each other in the direction of thickness is determined on the basis of the results of the observation by the naked eye. Accordingly, the variation in measurement is large and it takes long to determine the middle point.